title: Long-term incubation with proteasome inhibitors (PIs) induces IκBα degradation via the lysosomal pathway in an IκB kinase (IKK)-dependent and IKK-independent manner.
abstract: Proteasome inhibitors (PIs) have been reported to induce apoptosis in many types of tumor. Their apoptotic activities have been suggested to be associated with the up-regulation of molecules implicated in pro-apoptotic cascades such as p53, p21(Waf1), and p27(Kip1). Moreover, the blocking of NF-κB nuclear translocation via the stabilization of IκB is an important mechanism of PI-induced apoptosis. However, we found that long-term incubation with PIs (PS-341 or MG132) increased NF-κB-regulated gene expression such as COX-2, cIAP2, XIAP, and IL-8 in a dose- and time-dependent manner, which was mediated by phosphorylation of IκBα and its subsequent degradation via the alternative route, lysosome. Overexpression of the IκBα superrepressor (IκBα-SR) blocked PI-induced NF-κB activation. Treatment with lysosomal inhibitors (ammonium chloride or chloroquine) or inhibitors of cathepsins (Z-FF-FMK or Z-FA-FMK) or knock-down of LC3B expression by siRNAs suppressed PI-induced IκBα degradation. Furthermore, we found that both IKK-dependent and IKK-independent pathways were required for PI-induced IκBα degradation. Pretreatment with IKKβ specific inhibitor, SC-514, partially suppressed IκBα degradation and IL-8 production by PIs. Blockade of IKK activity using insolubilization by heat shock (HS) and knock-down by siRNAs for IKKβ only delayed IκBα degradation up to 8 h after treatment with PIs. In addition, PIs induced Akt-dependent inactivation of GSK-3β. Inactive GSK-3β accelerated PI-induced IκBα degradation. Overexpression of active GSK-3β (S9A) or knock-down of GSK-3β delayed PI-induced IκBα degradation. Collectively, our data demonstrate that long-term incubation with PIs activates NF-κB, which is mediated by IκBα degradation via the lysosome in an IKK-dependent and IKK-independent manner.
authors.affiliation: From the Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine; the Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea; the Lung Institute, Medical Research Center, Seoul National University College of Medicine, Seoul 110-799, Korea.
authors.forename: Kyoung-Hee
authors.initials: KH
authors.lastname: Lee
authors.affiliation: From the Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine; the Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea; the Lung Institute, Medical Research Center, Seoul National University College of Medicine, Seoul 110-799, Korea.
authors.forename: Jiyeong
authors.initials: J
authors.lastname: Jeong
authors.affiliation: From the Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine; the Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea; the Lung Institute, Medical Research Center, Seoul National University College of Medicine, Seoul 110-799, Korea. Electronic address: cgyoo@snu.ac.kr.
authors.forename: Chul-Gyu
authors.initials: CG
authors.lastname: Yoo
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D045744:Cell Line, Tumor; D004151:Dipeptides / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism*; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism*; D016209:Interleukin-8 / Q000096:biosynthesis / Q000235:genetics; D007659:Ketones / Q000494:pharmacology; D007976:Leupeptins / Q000494:pharmacology; D008247:Lysosomes / Q000235:genetics / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D059748:Proteolysis / Q000187:drug effects*; D011719:Pyrazines / Q000494:pharmacology; D013876:Thiophenes / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; C508606:CXCL8 protein, human; D004151:Dipeptides; D020672:I-kappa B Proteins; D016209:Interleukin-8; D007659:Ketones; D007976:Leupeptins; C502070:MAP1LC3B protein, human; D008869:Microtubule-Associated Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D061988:Proteasome Inhibitors; D011719:Pyrazines; C477523:SC 514; D013876:Thiophenes; D000072000:NF-KappaB Inhibitor alpha; C057383:MDL 201053; D000069286:Bortezomib; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051550:I-kappa B Kinase; D038362:Glycogen Synthase Kinase 3; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
keywords: Anticancer Drug; GSK-3β; IKK; IκB; Lung Cancer; Lysosome; Lysosomes; Proteasome; Proteasome Inhibitor; Signal Transduction